> We try to hide some of the differences between arches when reasonably feasible. e.g. Newer architectures no longer provide an open syscall, but do provide openat. We will still expose a sys_open helper by default that calls into openat instead.

Sometimes you actually want to make sure that the exact syscall is called; e.g. you're writing a little program protected by strict seccomp rules. If the layer can magically call some other syscall under the hood this won't work anymore.